Many adjusting devices of this type have already been disclosed, in most cases incorporated directly into bracelet clasps.
By way of example, patent application EP 1378185 A1 describes such a device which may or may not be incorporated into a bracelet clasp. This device has a frame with means for attachment to a bracelet, at one of its ends. An adjusting element is mounted so that it can slide in the frame and is provided with a plate in which a rack is formed. Jaws which can be actuated by push buttons are arranged in the frame so as to interact with the notches of the rack and lock the adjusting element in the desired position.
Thus, as with all known adjusting devices of this type, a user who wishes to alter the length of his bracelet must press the push buttons in order to free the adjusting element and then act on the bracelet, in order to lengthen or shorten it by displacing the adjusting element with reference to the frame of the device. Generally, the teeth of the rack are asymmetrical and oriented in such a way that the user can shorten his bracelet without having to free the rack by actuating the push buttons.
Alternative adjusting devices were known before, such as for example in the patent U.S. Pat. No. 1,997,836, in which a jaw acts on a rack so as to define distinct adjustment positions. This document provides that two blades are mounted so that they can slide relative to each other, with a spring placed between them, in such a way that, when the rack is freed, the two blades are placed in a relative position such that the length of the device is at its maximum. The user must then take hold of the two blades, bring them together and reduce the length of the device as required.
However, even when the device only needs to be adjusted by a few increments of the rack, the whole procedure must nevertheless be followed, including necessarily the stage with the configuration of the maximum length, which is not very convenient in practice.